An increasing amount of evidence points to a possible defect in oxidative metabolism in patients with certain inherited neurological disorders. Thus, a defect in the pyruvate oxidation system has been shown in some patients with lactic acidemia and diffuse neurologic disease, of the mitochondrial malic enzyme in patients with Friedreich's ataxia, and a partial deficiency of glutamate dehydrogenase in some patients with olivopontocerebellar degeneration. However, there is much controversy about the exact enzymatic defect(s). The objective of this project is the elucidation of the defect in some of these patients or in skin fibroblasts derived from such patients. For this purpose we are assaying a number of mitochondrial and non-mitochondrial enzymes in fibroblasts or leukocytes and we have initiated electron microscopic studies of the mitochondria. We became interested in the oxidative metabolism of mycoplasmas because mycoplasma contamination of fibroblast cultures interfered with the assay of pyruvate dehydrogenase complex in these cells. The oxidative metabolism of mycoplasmas is poorly understood. Hopefully, the elucidation of the defect in these diseases will help in the diagnosis and therapeutic intervention in the patients. Knowledge of the physiology of mycoplasmas may help in understanding the pathogenicity of these organisms.